There were 1,274 sightings of drones flying too close to other aircraft, people and buildings reported to the Federal Aviation Administration from February through September last year, the agency said in an e-mailed statement. That was 400 more incidents than the same period in 2015.

While the reports contained several claims that drones had hit traditional aircraft, the FAA wasn’t able to verify any collisions. Every investigation so far has found the collisions involved birds or other items, the agency said.

“Safely integrating unmanned aircraft into the national airspace system is one of the FAA’s top priorities, and the agency wants to send a clear message that operating drones around airplanes and helicopters is dangerous and illegal,” the agency said in the release. “Unauthorized operators may be subject to stiff fines and criminal charges, including possible jail time.”